1. Field of the Invention
The present invention relates to the field of LED luminous structures, and more particularly to the LED luminous structure for backlight source, which restricts the particle size of phosphor and the feature of encapsulation to achieve the effects of improving the light emitting efficiency and color light yield and preventing the oxidation of the phosphor effectively.
2. Description of the Related Art
Due to the excellent features of semiconductor light emitting components, these components are used extensively as a light source for display and illumination in industries. At present, a light emitting diode (LED) is generally used in the design of the light source for display and illumination, and the design requirement is to improve and provide an illumination effect similar to the daylight effect and different features of light color rendering. Up to now, various high-brightness single chip light emitting diodes have been developed, but present single chip LEDs can emit monochromatic light of a narrowband only due to the band gap of materials. Since the LED can emit a light with a fixed tone, therefore it is necessary to use the color mixing principle of chromatology to show the display and illumination effects of a white light.
At present, a white light source is mainly composed of a plurality of independent LED chips (KGB) that mixes three primary colors or uses the complementary color light mixing effect of a phosphor and the LED chips to show the white light. For example, Nichia Corporation adopts an InGaN series of blue light emitting chips to manufacture yellow phosphor of YAG and excite the yellow phosphor by a blue light to achieve a white light source through the complementation and mixing effects of the color lights. Regardless of the methods used for achieving the white light effect, it is necessary to improve the white light up to a level similar to the actual daylight.
As a backlight source for illumination or display, the color light rendering yield including the color temperature, color rendering coefficient and color gamut/saturation of a light source module must come with a specification to further simulate the true color effect. In addition to the color light rendering, the overall light emitting conditions such as the brightness are also an important element. Most conventional backlight sources of a display adopt a blue LED chip to work together with a yellow phosphor and use the principle of color light complementation to compose a blue light and a yellow light, and thus featuring a low cost and an excellent light emitting efficiency. However, this way of showing a white light includes mixing the blue light and the yellow light with each other, so that the composition of the green light and the red light is too little, and thus causing insufficient color light rendering. Some of the white light source structures use a blue LED chip to operate with a red phosphor and a green phosphor and mixing the three primary color lights to overcome the issue of insufficient light rendering. Regardless of which phosphor is used together with the chip to form the white light source, the properties of the phosphor such as the light absorption strength of the LED chip, the conversion rate of the absorbed light, the stability affected by humidity and heat, the uniformity of particle size will affect the final white light display effect of the light source. As described above, the LED chip operated together with the phosphor is used extensively for white light display or illumination, so that it is an important issue for related manufacturers to utilize the conditions of the phosphor and LED to improve the final effects of the light source including uniformity, color rendering coefficient, color saturation and light emitting efficiency.
In addition to the properties of the phosphor having substantial effects on the color light and the light emitting efficiency, the composition of most present phosphors uses metal ions as an activating agent, and the metal ions are oxidized by moisture easily, so that after the LED light source structure is packaged, it is an important subject to prevent the phosphor from being oxidized easily or affecting the formation of the white light source with the LED chip.
Therefore, the inventor of the present invention designed and developed an LED luminous structure for backlight source that restricts the particle size of the phosphor and the properties of the encapsulation, so that the LED structure provides high light emitting efficiency and wider color gamut, and prevent the activation of phosphor that produces a deviation or finally affects the white light rendering effect caused by oxidation.